1 research outputs found
Fungal Biotransformation of Insoluble Kraft Lignin into a Water Soluble Polymer
Low
substrate solubility and slow decomposition/biotransformation
rate are among the main impediments for industrial scale lignin biotreatment.
The outcome and dynamics of kraft lignin biomodification by basidiomycetous
fungi, <i>Coriolus versicolor</i>, were investigated in
the presence of dimethyl sulfoxide (DMSO). The addition of 2 vol %
DMSO to aqueous media increased the lignin solubility up to 70%, while
the quasi-immobilized fungi (pregrown on agar containing kenaf biomass)
maintained their ability to produce lignolytic enzymes. Basidiomycetous
fungi were able to grow on solid media containing both 5â25
g/L lignin and up to 5 vol % DMSO, in contrast to no growth in liquid
media as a free suspended culture. When a fungal culture pregrown
on agar was used for lignin treatment in an aqueous medium containing
2â5% DMSO with up to 25 g/L lignin, significant lignin modification
was observed in 1â6 days. The product analysis suggests that
lignin was biotransformed, rather than biodegraded, into an oxygenated
and cross-linked phenolic polymer. The resulting product showed the
removal of phenolic monomers and/or their immediate precursors based
on gas chromatography and thermal desorptionâpyrolysisâgas
chromatographyâmass spectrometry analyses. Significant intramolecular
cross-linking among the reaction products was shown by thermal carbon
analysis and <sup>1</sup>H NMR spectroscopy. An increase in polarity,
presumably due to oxygenation, and a decrease in polydispersity of
the lignin treatment product compared to untreated lignin were observed
while using liquid chromatography